Liquid molding processes require molding resins to be injected into a closed mold in a liquid state where the liquid resins are hardened into a molded plastic article. During the injecting step, air in the mold is displaced and forced out of the mold cavity through vents. The displaced air is ordinarily vented to the exterior of the closed mold. If air is not permitted to escape or otherwise ventilate from the mold cavity, the non-ventilated air will inhibit resin flow within the mold cavity, become entrained in the fluid resin, and remain trapped within the molded article, possibly causing a defective or scrap molded article.
Prior systems for venting closed molds ordinarily consist of channels cut into the mold through the tool parting line, or hoses from vent sprues, or the air is simply allowed to bleed out under pressure through the perimeter seal of the mold.
The prior art processes, however, frequently release displaced gases and waste material into the environment. Further operating problems include the inability to accurately and consistently control filling of the mold cavity as well as the inability to build constant pressure in the mold cavity due to uncontrolled open ventilation. Also, the prior art venting apparatus generally do not include self-contained cleaning means operative to clean the mold means of resin or other waste debris after the vent is closed.